Digital Video Tape Recorders Research Articles

Characterization of Digital Recording Channels by Means of Echo Cancellation Techniques

A simple yet accurate method is described for characterizing digital recording channels in terms of linear and nonlinear intersymbol interference and noise. The method is based on echo cancellation techniques, enables recorder operating conditions close to actual use, and delivers a joint portrait of the disturbances rather than isolated assessments. Experimental results for a high-density digital video tape recorder are included. >

High Speed Data Recording: Digital VTRs Find New Applications

Entertainment production, be it cinema, television, or even “game” software, is turning increasingly to computer-generated or manipulated information. Computer processing and digital manipulation has permitted the creation of images otherwise impossible, the production of effects not otherwise practical, and correction of innumerable image defects large and small. Given this combination of voluminous data and expensive hardware, the industry faced a dilemma: how to “move” jobs in and out of a facility quickly so the equipment could be made available to other clients and projects. Existing small format data recorders generally have proven unsatisfactory for these purposes due to the limited data rates and media size. Current digital videotape recorders are now capable of data rates well in excess of 200 Mbits/sec (25 Mbytes/sec). Unfortunately, some recorders incorporate data compression, rendering them suitable only for traditional video. Other video formats have been customized and repurposed for data recording, hut these machines are no longer applicable for video recording. As the boundaries between the computer and video worlds blur, users need multipurpose solutions for both fast data storage of nonrasterized image information and high-quality conventional video storage. Full bit-rate uncompressed digital video recorders can provide the desired performance capabilities for both video and high-performance data recording, allowing dual-purpose use of the same transport and cassettes. Panasonic developed the D-5 (uncompressed 10-bit ITU-R 601) videotape recorder (VTR) format for high-end video post-production, and it has met with wide acceptance. The Viewgraphics (Mountain View, Calif.) “Dataview” is an industry-standard computer bus (VME) interface device developed to allow large data files to be recorded on unmodified D-5 VTRs and to allow video to be input as data into platforms like the Silicon Graphics Onyx and Challenge. This paper describes the D-5 format, the Viewgraphics Dataview adaptor, and data recording on videotape.

Time-Resolved High-Resolution Electron Microscopy of Clusters, Surfaces, and Interfaces

Nanoscale materials show a variety of interesting physical and chemical properties. Since the properties are mostly determined by mesoscopic- and atomicscale areas of the materials, characterization of nanoscale materials at the atomic level is crucial for understanding the origin of their properties as well as for tailoring them to industrial needs. High-resolution electron microscopy (HREM) is an effective method to observe atomic structures in nanophase materials. The “structure-imaging technique,” originated by Ueda et al., and Cowley and Iijima, contributed much to the development of the method. Innovations are anticipated in (1) three-dimensional analysis of nanophase materials in real space, (2) observation of dynamic phenomena, and (3) extraction of compositional and physical information from nanometer-sized areas. Using the structure-imaging technique, one can observe directly nanometer-scale particles and defect structures such as voids and line and plane defects in crystals, including surfaces and interfaces. There were previously some limitations on the study of the dynamic process on the atomic level since images were captured on films. The recent development of high-sensitivity silicon-integrated-target-television (SIT-TV) cameras has initiated a new stage of HREM.Our time-resolved-high-resolution-electron-microscopy (TRHREM) system is composed of a 200-kV HREM (JEOL: JEM-2010) equipped with a high-sensitivity SIT-TV camera, various types of dedicated sample holders, an ultrahigh-vacuum (UHV) sample-preparation chamber, and a digital videotape recorder, as partly illustrated in Figure 5. The HREM images at 0.8–1.0-million magnification are recorded on the videotape recorder. In the U.S.-Japan TV system, one “frame image” of 1/30-s time resolution is composed of two interlaced “field images” of 1/60-s time resolution. The digital videotape recorder enables us to output the two “field images” separately from two frame memories.

Multilayers and Perovskites Rewrite Rules of Resistance

10 years ago, Peter Gr&uumlnberg of the J&uumllich Research Center in Germany discovered a metallic structure that did not seem to obey the ubiquitous Ohm's law. He constructed a sandwich of two iron layers separated by a thin film of chromium and found that at constant voltage he could vary the current through it simply by applying a magnetic field. The resistance of the structure was no longer a constant. Even greater changes of resistance in magnetic fields were soon found in complex oxides called manganese perovskites, closely related to high-temperature superconductors. These phenomena offer tantalizing prospects for applications such as reading heads in hard disk drives and digital videotape recorders and commercial devices are coming soon.

Architectures for MPEG compressed bitstream scaling

The idea of moving picture expert group (MPEG) bitstream scaling relates to altering or scaling the amount of data in a previously compressed MPEG bitstream. The new scaled bitstream conforms to constraints that are not known nor considered when the original preceded bitstream was constructed. Numerous applications for video transmission and storage are being developed based on the MPEG video coding standard. Applications such as video on demand, trick-play track on digital video tape recorders (VTR's) and extended-play recording on VTR's motivate the idea of bitstream scaling. In this paper, we present several bitstream scaling methods for the purpose of reducing the rate of constant bit rate (CBR) encoded bitstreams. The different methods have varying hardware implementation complexity and associated trade-offs in resulting image quality. Simulation results on MPEG test sequences demonstrate the typical performance trade-offs of the methods.

Digital video recording

Through mutual technology transfer between consumer and professional video recorders, the last 20 years has witnessed a rapid evolution from analog to digital recording. Each new digital videotape recorder (VTR) uses different channel coding. This implies that improving the recording density involves the development of new channel-coding schemes together with evolutionary magnetic tapes and heads. As a result, professional digital VTR's offer the best features for video recording. This paper reviews state-of-the-art magnetic recording devices, signal processing techniques for digital recording. It also describes the specifications for home-use digital recorders for current television systems, and discusses disk recording technology in the future. >

Emerging magnetic technologies for consumer audio/video (invited)

In the field of consumer audio/video, digital technology is the natural path for advancement. In audio systems, it has just been introduced in the form of digital compact cassette tape recorder and mini disk system in which magneto-optical recording is used. Therefore, the digital video instruments, such as small cassette digital video tape recorders (VTR) for high-definition television and static or short moving image devices will be the next attractive goals to be achieved. Technology analysis shows that the basic techniques of signal processing for small cassette VTR, in which the recording density of 1 μm2/bit and the data rate of 130–160 Mb/s are required, are almost at hand. For the media, improved metal-evaporated tape including oblique incident Co-CoO will be the most favorable candidate, although particulate media of metal powder tape (including Co or N modified forms) or Ba-ferrite tape coated by using the newly developed ultrathin coating techniques may take its position with the help of enhanced head sensitivity, because of their better durability. The basic demand for increasing saturation induction Bs of the head materials will be fulfilled by fine grain Fe-based materials, the available Bs being as high as 2 T. A dramatic increase in magnetoresistive (MR) head sensitivity is expected by using the giant MR effect, although a breakthrough is required to extract its full potential. On the other hand, varieties of static (including short moving) image devices will be developed by use of rapidly progressing magneto-optical recording technology. Preliminary techniques are now ready to meet the demand for the required increase in bit rate and recording density. A bit rate of 64 Mbits/s (8 Mbytes/s) has already been attained. A bit density of 107 bits/mm2 (6.5 Gb/in.2) is likely to be realized, and a factor of 2 or 3 more enhancement can be counted on. Rigid disk and perpendicular recording will have a chance to participate in the field if their techniques are applied to removable media.

Multiresolution high-definition television compression algorithm for digital video tape recording

A new scheme is proposed for the efficient coding of highdefinition television (HDTV) sequences for digital video tape recording. This scheme allows the variable speed playback of recorded material at speeds up to 100 times normal in both the forward and reverse directions. An 8:1 level of compression of the original HDTV data is obtained by exploiting both intraframe and interframe redundancies during the coding process, although the perceptual quality of the reconstructed sequences is uncompromised. To allow the high-quality playback of the recorded data at very high speeds, a hierarchical data structure is employed and the head-positioning capabilities of conventional digital video tape recorders (DVTRs) are exploited to enable the recovery of perceptually vital information at high tape speeds. The performance of the resuIting scheme is examined by simulating the compression and reconstruction of three HDTV sequences at 1, 10, 20, 50, and 100 times normal playback speed.

Fast scan technology for digital video tape recorders

A solution to the problems of implementing trick play on a compressed digital VTR (video tape recorder) is described. Because of loss of data in the fast-forward/fast-reverse playback, it is difficult to decode a useful image from the data recovered, and image quality is poor. The authors' proposal reserves an area on the tape which will be traversed during trick playback; a subset of the bitstream which is specifically adapted to trick play in this track is recorded. Thus, good-quality trick play is achieved without impact on normal playback and without decoding and recording the compressed bitstream.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An HDTV compression scheme for production-quality recording and high-performance shuttle operation

A novel scheme is proposed for the efficient coding and compression of high-definition television (HDTV) sequences for recording on digital video tape. The scheme achieves a constant 8:1 compression ratio by exploiting both intraframe and interframe compression techniques and removing both statistical and psychovisual redundancies during the coding process. However, a perceptually lossless image quality is still maintained after both single and multiple generations. This scheme also allows the recognizable playback of recorded material at speeds up to 50 times normal in both the forward and reverse directions. This high-performance picture-in-shuttle mode of operation is accomplished by employing a hierarchical data structure and exploiting the head-positioning capabilities of conventional digital video tape recorders. The performance of the overall recording scheme is evaluated by simulating the compression and reconstruction of three HDTV test sequences at 1, 10, 20 and 50 times normal layback speed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Record/playback interfaces: DSC-HDTV, HD-VCR and D3 VTR

Three interface systems used to record and play back the compressed digital data from the DSC-HDTV (high-definition television) system are described. The first interface is for recording the compressed data from the DSC-HDTV to the HD-VCR system; the second is for the DSC-HDTV to the D3 digital VTR (video tape recorder); and the third is for the HD-VCR to the D3 VTR. The interface hardware was fully developed, and the feasibility of recording and playing back the digital data from the DSC-HDTV to both the HD-VCR and the D3 machine was demonstrated. >

Playback Video Processing for a Composite Digital Videotape Recorder

The production videotape recorder (VTR) has, for some time, been expected to support many modes of operation other than normal play and record. These “off-speed” VTR modes include variable play, time compression, and still frame. To make this possible the output video signal must be passed through a video processing stage. Other uses for the output video processing electronics include the playback of noncolor frame edits and adjustment of chrominance gain and phase. While operating in these modes the television signal must be decoded to separate the chrominance and luminance, so that chrominance inversion and vertical interpolation can be applied to the signal to convert from an incoming field of one type to an outgoing field of a different type. This article describes the video playback processing used in a digital VTR where exceptional quality is required, and details are given of some improved methods of modifying the signal in a composite environment using 4f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</inf> data sampling.

Audio Editing in the 1/2-in. D-3 Digital VTR

Analog VTRs, such as Betacam or MII, are among the most common media in broadcasting or studio use for recording analog video and audio. The actual recording device in these videotape recorders (VTRs) is a stationary head for audio recording. Digital VTRs, such as D-1 or D-2, record video and audio digitally, and this method has achieved a tremendous improvement in performance. The latter is quickly becoming the main method of tape recording today. However, the drawback in digital recording is that editing in the audio channel is not easily performed. This article will report on basic recording principles that allow the best use of digital audio recording in commercially available 1/2-in. composite digital VTRs, such as D-3.

Improvement of Picture Quality in Nonstandard Speed Play of a Digital VTR

In the nonstandard speed play of a composite videotape recorder (VTR), the reproduced video is converted to a standard TV signal, since fields in the reproduced video are skipped or repeated. In the field-conversion processing, a Y/C separation circuit and a line-interpolation circuit are used. In a conventional processor, the picture quality is deteriorated due to vertical displacement of the image and lower resolution. To remove these deficiencies a motion-adaptive field-conversion circuit, which uses interfield signals, has been developed. Based on these techniques, three kinds of gate arrays were developed and employed in a D-2 VTR for NTSC signals. Consequently, these problems were solved and the picture quality was remarkably improved.

Digital tape recording in ATV video formats using the commercially available 1125 line recorders

Six advanced television (ATV) transmission systems are being tested. These systems provide video signal inputs in the form of red (R), green (G), and blue (B) in analog form. One system requires 1125-line, 60-field/s interlaced video, two require 1050-line, 59.94-field/s interlaced video, two require 787.5-line 59.94-field/s noninterlaced video, and one requires 525-line, 59.94-field/s noninterlaced video. Digital video tape recording of RGB video in all proposed ARV formats has been implemented on the digital video tape recorder (DVTR), which was designed for the SMPTE-240-M video format. This required the development of a format converter, which is described. >

Signal processing for future home-use digital VTR's

The author considers, mainly from the viewpoint of signal processing technologies, the current efforts for future home-use digital videotape recorders (VTRs). Recording technologies for future home-use digital VTRs are reviewed with respect to both current TV and HDTV systems. High-density recording and bit rate reduction are the major technologies needed for digital video recording with small cassettes. Recent experiments show that the technical problems, except those of equipment size and cost, have almost been solved. >

Optimization of azimuth angle for some kinds of media on digital VCRs

A method to determine an optimum azimuth angle in a digital video tape recorder is demonstrated together with consideration made for ME (metal evaporated), MP (metal particulated), and Ba-ferrite tapes. The optimum azimuth angle is derived by comparing the value of theoretically and experimentally derived signal-to-noise ratios (SNRs) at the detecting point of a video cassette recorder with the value of theoretically derived SNR required to achieve a desired bit error rate under crosstalk interference from adjacent tracks. Not only azimuth angle but also bit length and track pitch for maximizing a real recording density are simultaneously derived by the method. The relationship between the optimum azimuth angle and orientation of the tapes is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Rate-constrained optimal block-adaptive coding for digital tape recording of HDTV

An image coding algorithm for digital video tape recorders (DVTR) must satisfy several requirements which do not arise in other applications of video compression. A key constraint on the data format is satisfied if every frame (or field) of video is partitioned into a small number of subimages, each independently coded with a fixed number of bits. This requirement excludes the use of interframe coding and most variable-rate image coding algorithms. We propose to use a new algorithm that codes a subimage efficiently under this data format constraint and allows virtually lossless reproduction at reasonable low bit rates. Each subimage is partitioned into non-overlapping blocks and each block is coded by one of a finite set of predesigned block quantizers covering a range of bit rates. For the ith block in the subimage, a rate function Ri(Li) and a distortion function Di(Li) is tabulated for each block quantizer Li. A near-optimal quantizer allocation algorithm based on the Lagrange Multiplier method is used to select a particular quantizer for each block. The objective is to minimize the distortion of the entire subimage under the constraint on the total number of bits for the subimage. A system for the compression of HDTV for DVTR's based on this rate-constrained optimal block-adaptive technique is designed using the DCT and vector quantization with a multistage structure. Simulation results demonstrate that this algorithm has the potential of achieving virtually lossless compression for digital tape recording of HDTV.

A simulation study of adaptive reception schemes for high-density digital magnetic storage

At high information densities, digital magnetic recording systems may be seriously hampered by channel imperfections such as intersymbol interference, noise, fading, nonlinearities, crosstalk, and overwrite noise. For such compound disturbance constellations, theoretical analysis of receiver performances becomes difficult. As an alternative, the digitized output signal of an experimental high-density digital videotape recorder is used to compare various promising receiver types by simulation. Apart from adaptive versions of the linear and decision feedback equalizers, adaptive variants of the Viterbi detector are studied, including new ones with resistance to nonlinearities and channel fading. Improvements of up to about 5 dB in effective signal-to-noise ratio over nonadaptive linear equalization are found to be within reach under worst-case operating conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characterization of digital recording channels by means of echo cancellation techniques

A simple yet accurate method is described for characterizing digital recording channels in terms of linear and nonlinear intersymbol interference and noise. The method is based on echo cancellation techniques, enables recorder operating conditions close to actual use, and delivers a joint portrait of the disturbances rather than isolated assessments. Experimental results for a high-density digital video tape recorder are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>